From 0bb9dd82661856f86e9ace1d61911f298c27fbe2 Mon Sep 17 00:00:00 2001
From: Akshat Lakhera <akshatlnct2024@gmail.com>
Date: Mon, 19 Oct 2026 16:16:15 +0700
Subject: [PATCH 1/2] LegalizeJSInterface: pick unique names for generated
 stubs

Signed-off-by: Akshat Lakhera <akshatlnct2024@gmail.com>
---
 src/passes/LegalizeJSInterface.cpp            | 15 +++--
 .../legalize-js-interface-name-collision.wast | 55 +++++++++++++++++++
 2 files changed, 62 insertions(+), 8 deletions(-)
 create mode 100644 test/lit/passes/legalize-js-interface-name-collision.wast

diff --git a/src/passes/LegalizeJSInterface.cpp b/src/passes/LegalizeJSInterface.cpp
index 4bb74918ff0..c8354962d91 100644
--- a/src/passes/LegalizeJSInterface.cpp
+++ b/src/passes/LegalizeJSInterface.cpp
@@ -33,6 +33,7 @@
 #include "ir/element-utils.h"
 #include "ir/import-utils.h"
 #include "ir/literal-utils.h"
+#include "ir/names.h"
 #include "ir/utils.h"
 #include "pass.h"
 #include "shared-constants.h"
@@ -269,12 +270,14 @@ struct LegalizeJSInterface : public Pass {
   Function* makeLegalStubForCalledImport(Function* im, Module* module) {
     Builder builder(*module);
     auto legalIm = std::make_unique<Function>();
-    legalIm->name = Name(std::string("legalimport$") + im->name.toString());
+    legalIm->name = Names::getValidFunctionName(
+      *module, Name(std::string("legalimport$") + im->name.toString()));
     legalIm->module = im->module;
     legalIm->base = im->base;
     legalIm->hasExplicitName = true;
     auto stub = std::make_unique<Function>();
-    stub->name = Name(std::string("legalfunc$") + im->name.toString());
+    stub->name = Names::getValidFunctionName(
+      *module, Name(std::string("legalfunc$") + im->name.toString()));
     stub->type = im->type.with(Exact);
     stub->hasExplicitName = true;
 
@@ -309,12 +312,8 @@ struct LegalizeJSInterface : public Pass {
       Type(Signature(Type(params), call->type), NonNullable, Inexact);
 
     auto* stubPtr = stub.get();
-    if (!module->getFunctionOrNull(stub->name)) {
-      module->addFunction(std::move(stub));
-    }
-    if (!module->getFunctionOrNull(legalIm->name)) {
-      module->addFunction(std::move(legalIm));
-    }
+    module->addFunction(std::move(stub));
+    module->addFunction(std::move(legalIm));
     return stubPtr;
   }
 
diff --git a/test/lit/passes/legalize-js-interface-name-collision.wast b/test/lit/passes/legalize-js-interface-name-collision.wast
new file mode 100644
index 00000000000..1c9576e2c2d
--- /dev/null
+++ b/test/lit/passes/legalize-js-interface-name-collision.wast
@@ -0,0 +1,55 @@
+;; NOTE: Assertions have been generated by update_lit_checks.py --all-items and should not be edited.
+;; RUN: wasm-opt %s --legalize-js-interface -S -o - | filecheck %s
+
+;; The module already has functions named like the ones the pass would create
+;; for the illegal import. The pass must pick fresh names instead of reusing
+;; (or failing to add) the existing ones.
+
+(module
+ (import "env" "imp" (func $imp (param i64) (result i32)))
+ ;; CHECK:      (type $0 (func (param i64) (result i32)))
+
+ ;; CHECK:      (type $1 (func (result f32)))
+
+ ;; CHECK:      (type $2 (func (result i32)))
+
+ ;; CHECK:      (type $3 (func (param i32 i32) (result i32)))
+
+ ;; CHECK:      (import "env" "imp" (func $legalimport$imp_4 (param i32 i32) (result i32)))
+
+ ;; CHECK:      (func $legalfunc$imp (param $0 i64) (result i32)
+ ;; CHECK-NEXT:  (i32.const 7)
+ ;; CHECK-NEXT: )
+ (func $legalfunc$imp (param i64) (result i32)
+  (i32.const 7)
+ )
+ ;; CHECK:      (func $legalimport$imp (result f32)
+ ;; CHECK-NEXT:  (f32.const 8)
+ ;; CHECK-NEXT: )
+ (func $legalimport$imp (result f32)
+  (f32.const 8)
+ )
+ ;; CHECK:      (func $f (result i32)
+ ;; CHECK-NEXT:  (call $legalfunc$imp_4
+ ;; CHECK-NEXT:   (i64.const 1)
+ ;; CHECK-NEXT:  )
+ ;; CHECK-NEXT: )
+ (func $f (result i32)
+  (call $imp
+   (i64.const 1)
+  )
+ )
+)
+;; CHECK:      (func $legalfunc$imp_4 (param $0 i64) (result i32)
+;; CHECK-NEXT:  (call $legalimport$imp_4
+;; CHECK-NEXT:   (i32.wrap_i64
+;; CHECK-NEXT:    (local.get $0)
+;; CHECK-NEXT:   )
+;; CHECK-NEXT:   (i32.wrap_i64
+;; CHECK-NEXT:    (i64.shr_u
+;; CHECK-NEXT:     (local.get $0)
+;; CHECK-NEXT:     (i64.const 32)
+;; CHECK-NEXT:    )
+;; CHECK-NEXT:   )
+;; CHECK-NEXT:  )
+;; CHECK-NEXT: )

From 19abeb599d36a75cc719d8865638777488eee175 Mon Sep 17 00:00:00 2001
From: Akshat Lakhera <akshatlnct2024@gmail.com>
Date: Mon, 19 Oct 2026 17:36:47 +0700
Subject: [PATCH 2/2] Use the pointer returned by addFunction

Signed-off-by: Akshat Lakhera <akshatlnct2024@gmail.com>
---
 src/passes/LegalizeJSInterface.cpp | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/src/passes/LegalizeJSInterface.cpp b/src/passes/LegalizeJSInterface.cpp
index c8354962d91..c1aa9a8af8d 100644
--- a/src/passes/LegalizeJSInterface.cpp
+++ b/src/passes/LegalizeJSInterface.cpp
@@ -311,8 +311,7 @@ struct LegalizeJSInterface : public Pass {
     legalIm->type =
       Type(Signature(Type(params), call->type), NonNullable, Inexact);
 
-    auto* stubPtr = stub.get();
-    module->addFunction(std::move(stub));
+    auto* stubPtr = module->addFunction(std::move(stub));
     module->addFunction(std::move(legalIm));
     return stubPtr;
   }